fix(lint): restore noqa directives and register custom codes with ruff

Reverts the noqa: removal — the architecture validators (SVC-006,
SEC-034, MOD-004, API-007) use these to skip known-safe violations.
Added ruff lint.external config so ruff treats them as valid codes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/core/routes/api/admin_menu_config.py

@@ -28,7 +28,7 @@ from app.api.deps import (
     get_db,
 )
 from app.modules.core.services.menu_service import MenuItemConfig, menu_service
-from app.modules.enums import FrontendType  # API-007 - Enum for type safety
+from app.modules.enums import FrontendType  # noqa: API-007 - Enum for type safety
 from app.modules.tenancy.services.platform_service import platform_service
 from app.utils.i18n import DEFAULT_LANGUAGE, translate
 from models.schema.auth import UserContext

app/modules/core/services/auth_service.py

@@ -61,7 +61,7 @@ class AuthService:
 
         # Update last_login timestamp
         user.last_login = datetime.now(UTC)
-        db.commit()  # SVC-006 - Login must persist last_login timestamp
+        db.commit()  # noqa: SVC-006 - Login must persist last_login timestamp
 
         token_data = self.auth_manager.create_access_token(user)
 
@@ -176,7 +176,7 @@ class AuthService:
 
         # Update last_login timestamp
         user.last_login = datetime.now(UTC)
-        db.commit()  # SVC-006 - Login must persist last_login timestamp
+        db.commit()  # noqa: SVC-006 - Login must persist last_login timestamp
 
         token_data = self.auth_manager.create_access_token(user)
 

app/modules/core/services/platform_settings_service.py

@@ -133,7 +133,7 @@ class PlatformSettingsService:
             )
             db.add(admin_setting)
 
-        db.commit()  # SVC-006 - Setting change is atomic, commit is intentional
+        db.commit()  # noqa: SVC-006 - Setting change is atomic, commit is intentional
         db.refresh(admin_setting)
 
         logger.info(f"Platform setting '{key}' set to '{value}' by user {user_id}")